Measurement of Heparin in Patients Receiving Subcutaneous Heparin Therapy

Heparin assays based on four different tests of clotting function have been compared with a heparin assay utilizing the potentiating effect of heparin on anti-factor Xa in a group of patients receiving subcutaneous heparin therapy during late pregnancy. It is considered that the anti-factor Xa method is a better indication of the antithrombotic effect of heparin. In the presence of high levels of clotting factors, heparin assays based on tests of clotting function can be misleading.